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Ligands based on a [1,4]dioxocino[6,5-b:7,8-b']dipyridine (doxpy) core were prepared and characterized. They all present two equal chelating moieties each one including one N, O, or S donor in addition to a pyridinic nitrogen. These ligands displayed high selectivity for the formation of binuclear complexes. At least one d(8) ion (Pd(II) or Pt(II)) complex was prepared for each type of ligand. The stereochemical behavior of the ligands is discussed on the basis of NMR spectra. Stable atropoisomers were obtained in the case of N-oxides or in case chiral centers were introduced in the ethereal bridge. As for the complexes, stable enantiomers appear to be in principle attainable for all the new compounds. A test on the cooperative ability of two Pd(II) centers has been grounded on the microstructure of the styrene/CO copolymer catalytically produced by a binuclear pyridine-imino complex. In fact, comparison with the microstructure of the copolymers produced by related single-site mono- and (open-chain) binuclear catalysts reveals significant difference, thus giving indication of possible synergic metal activity.

Two unprecedented types of ligands, with comparable essential coordination features, are proposed as supports for metal centres in bimetallic promotion of organic syntheses, including asymmetric catalytic processes. Synthesis and characterization of the bis-chelating bipyridine ligands A with C2 symmetry and X-ray analysis of one bipyridine diimine palladium binuclear complex are described. Synthesis and X-ray analysis of the bis-phenylimino derivative of a dibenzodioxepine dialdehyde are also reported. This dialdehyde is a key intermediate in the attainment of bis-isoquinoline ligands B with the same symmetry as A.

Cationic trigonal bipyramidal complexes of the type [PtRL(NN′)(olefin)]BF4 with various hydrocarbyl (R), neutral monodentate (L), and bidentate nitrogen (NN′) ligands have been prepared and characterized by elemental analysis, conductivity measurements, and 1H NMR spectroscopy. The coordination around PtII is trigonal bipyramidal, with the olefin and the NN′ ligand in equatorial positions. The reversible loss of the olefin is markedly affected by the nature of the apical ligand L, which also influences stereochemical aspects, and by the steric requirements of NN′.